Evolution: Forces that drive differentiation

Evolution: Forces that drive differentiation



This series of papers touch on many of the key concepts in Evolution, such as natural selection, sexual selection, speciation, barriers to gene exchange, hybrid zones, gene introgression, lateral gene transfer and adaptation.


The study system is the famous mimetic tropical Heliconius butterflies, which were first studied in the Amazon forest by the English naturalist Henry Walter Bates in the 1850’s. The papers follow a series of publications from James Mallet et al. starting in 1989 through 2012 and make use of various methodological approaches ranging from a traditional study of natural populations to next generation genomic sequencing.

Applicable for Courses:

Upper-level biology courses

Educational Level:

Upper-level (300-400 level)

Roadmap Objectives:

    • Article: Mallet J. & Barton, N. 1989. Strong Natural Selection in a Warning Color Hybrid Zone. Evolution 43(2): 421-431
    • Content area/major concepts: The first paper introduces hybrid zones, (their maintenance and stability), forces of migration and selection (focusing on frequency dependent selection), mimicry and basic genetics (dominant recessive, how many genes in a phenotypic trait). Opens opportunities to the discussion of what is a species (model is great to discuss morphological, biological and even phylogenetic species concepts).
    • Methods or technology used to obtain data: Traditional capture-recapture field study (with control and experimental groups), calculation of selection from field data, likelihood estimate of survivor rates.
    • How the CREATE strategy was used: To be determined.
    • Biggest teaching challenge: Difficult to read, experimental design is rather complicated, requires a good understanding of the system (there is a typo on methods of “gregarious roots” instead of “gregarious roosts”). Likelihood estimates of life expectance will be beyond most biology student math skills.
    • Article: Jiggins CD, Naisbit, RE, Coe, RL & Mallet, J. 2001. Reproductive Isolation caused by colour pattern mimicry. Nature 411: 302-305.
    • Content area/major concepts: The second paper introduces sexual selection, barriers to gene exchange, pre and post mating isolation and reinforcement. It opens up discussions about magic traits in speciation.
    • Methods or technology used to obtain data: Behavioral assays (mate choice), likelihood calculation of probability of mating.
    • How the CREATE strategy was used: To be determined.
    • Biggest teaching challenge: Again, understanding the log-likelihood calculations could be hard to the average biology student
    • Article: Baxter et al. 2010. Genomic Hotspots for Adaption: The Population Genetics of Mullerian Mimicry in the Heliconius melpomene clade. PLOS Genetics 6(2): e1000794
    • Content area/major concepts: The third paper makes use BAC tile path, and genetic mapping, gene expression, Linkage disequilibrium and population genetic structure across a hybrid zone to get into gene introgression, barrier genes, selective sweeps and age of a selective event. Also addresses insect development superficially.
    • Methods or technology used to obtain data: Population genetics, sanger sequencing, qPCR, genetic mapping,
    • How the CREATE strategy was used: To be determined.
    • Biggest teaching challenge: Very long and dense paper. First time students will be introduced to molecular genetics techniques and gene mapping, lots of new techniques in a single paper. Lots of supplementary information.
    • Article: The Heliconius Genomic Consortium. 2012. Butterfly genome reveals promiscuous exchange of mimicry adaptations among species. Nature
    • Content area/major concepts: The fourth paper is a genomic paper (whole genome sequencing) that makes use of gene genealogies (uncongruency) to test gene exchange between species. Also focus in gene syntheny of chemosensory genes and gene duplications in evolution. Opens an opportunity to discuss why not all gene genealogies are congruent with species trees and fine tune students understanding on phylogeny building.
    • Methods or technology used to obtain data: Phylogenetic reconstruction, RAD sequencing, 454 and Illumina sequencing.
    • How the CREATE strategy was used: To be determined.
    • Biggest teaching challenge: Dense paper (although short!), genomic technology will be challenging to students, methods are hidden in supplementary information. Supplementary information is enormous.

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